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Share-Based Payments (Details)
12 Months Ended
Apr. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Expected volatility (%) 20.70%
Dividend yield (%) 2.30%
Risk-free interest rate (%) 1.90%
Expected life of stock option (years) 5 years 10 months 24 days